Hydrogen Atom Transfer by a High-Valent Nickel-Chloride Complex.
Hydrogen Atom Transfer by a High-Valent Nickel-Chloride Complex.
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DOI：
10.1021/jacs.7b11953
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发表时间：
2018-01
影响因子：
15
通讯作者：
P. Mondal;P. Pirovano;Ankita Das;E. Farquhar;A. McDonald
中科院分区：
文献类型：
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作者：
P. Mondal;P. Pirovano;Ankita Das;E. Farquhar;A. McDonald
氧代-金属-卤化物部分通常被认为是C-H键活化氧化剂，末端氧代-金属实体被鉴定为亲电氧化剂。尚未研究金属卤化物物质的亲电反应性。我们通过[Ni Ⅱ（Cl）（L）]-前体的单电子氧化制备了高价镍卤化物配合物[Ni Ⅲ（Cl）（L）]（2，L = N，N '-（2，6-二甲基苯基）-2，6-吡啶二甲酰胺）。利用电子吸收光谱、电子顺磁共振、X射线吸收光谱和质谱对化合物2进行了表征。2容易与含有酚O-H或烃C-H键的底物反应。Hammett，埃文斯-波兰尼，马库斯之间的关系确定的速率常数和底物pKa，X-H键的解离能，和氧化电位，分别进行了分析。通过这种分析，我们发现2通过氢原子转移（HAT）机制反应。我们的研究结果照亮酶的高价氧代金属卤化物氧化剂和氧化卤化催化剂的设计开辟了新的途径。
Oxo-metal-halide moieties have often been implicated as C-H bond activating oxidants with the terminal oxo-metal entity identified as the electrophilic oxidant. The electrophilic reactivity of metal-halide species has not been investigated. We have prepared a high-valent nickel-halide complex [NiIII(Cl)(L)] (2, L = N,N'-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamide) by one-electron oxidation of a [NiII(Cl)(L)]- precursor. 2 was characterized using electronic absorption, electron paramagnetic resonance, and X-ray absorption spectroscopies and mass spectrometry. 2 reacted readily with substrates containing either phenolic O-H or hydrocarbon C-H bonds. Analysis of the Hammett, Evans-Polanyi, and Marcus relationships between the determined rate constants and substrate pKa, X-H bond dissociation energy, and oxidation potential, respectively, was performed. Through this analysis, we found that 2 reacted by a hydrogen atom transfer (HAT) mechanism. Our findings shine light on enzymatic high-valent oxo-metal-halide oxidants and open new avenues for oxidative halogenation catalyst design.